The skin is the first barrier to maintain the stability of internal environment of the body and resist harmful factors of external environment, and is easily damaged because of various external factors. When full-thickness skin defects reach a certain level, it is difficult for the skin to repair itself, so wound dressings are needed to promote wound healing. Seeking an ideal dressing that can promote wound healing has long been a hot research topic. Chitosan is a unique biopolysaccharide polymer with good biocompatibility, biodegradability, antibacterial activity, and thermal stability, which has great potential in the development and application of wound dressings. Based on the introduction of properties of chitosan, this article reviews the role and mechanism of chitosan-based wound dressings in wound healing, and summarizes the hemostatic effect, antibacterial effect, delivery effect, and tissue regeneration promotion effect of chitosan, aiming to provide a certain reference for the research and development of new chitosan-based wound dressings in the future.

Objective:To evaluate the mid-term outcomes of patients with rheumatic heart disease who underwent aortic valve repair surgery in a prospective cohort.Methods:From January 2016 to December 2020, a total of 54 patients with rheumatic heart disease underwent aortic valve repair surgery in Beijing Anzhen Hospital, with an average age of (50.61±13.29) years, including 29 females (53.7%). There were 31 patients (57.4%) had pure aortic insufficiency, 2 patients (3.7%) had pure aortic stenosis and 21 patients (38.9%) had mixed lesion. During the same period, 43 patients (80.0%) underwent mitral valve surgery, 36 patients (66.7%) underwent tricuspid valve surgery, and 20 patients (37.0%) underwent atrial fibrillation radiofrequency ablation.The follow-up period was from 1 month to 61 months (median follow-up was 25 months). Paired rank-sum test was used to compare the differences in continuous variables among subjects, and Kaplan- Meier method was used to analyze the clinical outcomes during the follow-up period. Results:Proportion of moderate and severe aortic regurgitation Preoperatively was higher than that of discharge data, aortic valve orifice maximum velocity and left ventricular end-diastolic diameter were significantly lower than discharge data (all P<0.05). The 5-year survival rate was (96.1±2.7)% (2 patients died). The 5-year freedom from reoperation after aortic valve repair was (89.5±4.5)%(5 patients underwent redo surgery). The 5-year freedom from valvular-related complications was (91.3±4.2)%(3 patients suffered from complications). Conclusion:Aortic valve repair surgery for rheumatic aortic valve disease is feasible and has excellent early and mid-term results, it can be a reliable treatment option.

Objective To investigate protective activity against Aβ25-35-induced cytotoxicity in PC12 cells of different extracts and ursolic acid, which were isolated from pyrola decorata. Methods Aβ25-35-induced cytotoxicity in PC12 cells was established as the model in vitro. The cultured PC12 cells were divided into blank control group, DMSO control group, model control group, different extract groups of pyrola decorate and ursolic acid(UA) group. The different extract groups included ether extract (PE), acetidin extract (AE), n-butanol extract (BE), the water extract (WE), 50% ethanol extract (HEE). MTT assay was used to test the optimum concentration, and the number of viable cells in culture medium was measured by ELISA at 490 nm wavelength. Results The cell viabilities in different extracts groups(PE, AE, BE, WE, HEE) were respectively 89.3%, 77.2%, 79. 2%, 75. 1% ,74. 0% at the concentration of 5. 0 mg ? mL-1 . Moreover, ursolic acid showed the best neuroprotective activity (88.9%) at the concentration of 500 μg?L-1 . Compared with model control group, the survival rate of each group was remarkably increased, and the protective activities of PE and UA were more significant among them. Conclusion Different polar extracts of pyrola decorata and isolated ursolic acid have neuroprotective effects on Aβ25-35-induced cytotoxicity in PC12 cells in certain degrees.

AIM: To investigate the effects of melatonin (MT) on the immunological function in colon of rats immunological colitis. METHODS: The rats colitis was produced by enema with trinitrobenzene sulfonic acid and ethanol. The experiment groups included normal group, model group, 5-aminosalicylic acid (5-ASA) group (100 mg?kg~(-1)), MT groups (2.5,5.0,10.0 mg?kg~(-1)), and treated intracolon with saline, saline, 5-ASA and MT respectively (once per day, from the d7 after the establishment of colitis model to the end of the experiment). The content of interleukin (IL-1, IL-2) and tumour necrosis factor (TNF)-? in rats colon were detected; The inflammatory colon were homogenatized and incubated with lipopolysaccharides (LPS), and designed as control group, model group, 5-ASA group (100?mol/L), MT groups(0.01, 0.1, 1.0 mmol/L). The content of IL-1, IL-2, TNF-?, nitric oxide (NO), lactic dehydrogenase (LDH), myeloperoxidase (MPO) and malondiadehyde (MDA) in the supernant were detected. RESULTS: In model group, the contents of IL-1, IL-2 and TNF-? in colon elevated remarkably and MT depressed this effectively. In the inflammatory colon homogenates of rats colitis, the content of IL-1, IL-2, TNF-?, NO, LDH, MPO and MDA elevated remarkably, Pretreation with MT depressed the content of IL-1, TNF-?, LDH, MPO and MDA effectively. MT (1.0mmol/L) also reduced the production of NO obviously. CONCLUSION: The abnormal immunological function is shown obviously in rats colitis. MT normalizes this change in vivo and in vitro and attenuates the mucosal damage.